Process for removing fuzz from polyester fabrics



Feb. 6, 1968 P. T. SCOTT 3,

PROCESS FOR REMOVING FUZZ FROM POLYESTER FABRICS Filed Jan. 20, 1966 WOVEN FABRIC CONTAINING POLYESTER STAPLE HAVING SURFACE HAIRS SINGEING FABRIC I I FABRIC HAVING POLYESTER MELT- BALLS TREATING WITH POLYESTER DISSOLVINC ACIDIC SOLVENT AT ZO-30C FABRIC CONTAINING SOLVENT WASHING FABRIC HAVING PLEASINC AESTHETICS WITH LOW-FILLING PROPENSITY INVENTOR PAUL T. SCOTT ATTORNEY United States Patent 3,367,003 PROCESS FOR REMOVING FUZZ FROM POLYESTER FABRICS Paul T. Scott, Kinston, N.C., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Jan. 20, 1966, Ser. No. 521,829 7 Claims. (Cl. 26-3) ABSTRACT OF THE DISCLOSURE In the finishing of textile fabrics Woven from staple spun yarns containing polyester fibers, the process of singeing the fabric to remove hairs with resultant formation of polyester melt balls, subsequently treating the singed fabric with a polyester dissolving acidic solvent at 20-30 C. to selectively dissolve the melt balls with negligible effect on the polyester fibers in the fabric, and washing the fabric to terminate the solvent treatment after dissolving the melt balls and before damaging the fibers.

This invention relates to a process for improving textile fabrics, and more specifically to a process for improving the properties of textile fabrics comprising spun polyethylene terephthalate staple yarn.

It is known that the removal of surface hairs or fuzz from fabrics comprising spun polyethylene terephthalate staple yarn improves the textile aesthetics thereof and reduces the tendency of the fabrics to pill. The removal of surface hairs in such fabrics is most practically effected in commercial operations by thermal surface-treatment. In the modern process, the fabric is passed near a flame to singe the fabric. This melts the surface hairs thereon. Although the singed fabric is improved in the aforementioned respects as compared to unsinged fabrics of similar makeup, it suffers from two serious defects which are directly related to the many melt-balls, i.e., highvouume, amorphous portions on the polyester fibers which invariably result from singeing operations. First, in fabricdyeing operations, the amorphous melt-balls absorb a greater amount of dyestuff than the portions of the polyester fiber which are molecularly oriented to a greater degree and are more crystalline, a phenomenon which results in an undesirable speckled appearance in the dyed fabric. Second, the melt-balls impart a harsh, undesirable surface handle to the fabric.

It has been proposed to remove surface fuzz from fabrics of spun polyethylene terephthalate staple yarn by treatment with strong hydrolyzing media, such as caustic, in order to avoid the difficulties associated with singeing treatments. However, these methods invariably result in the decomposition of base fiber simultaneously with decomposition of surface fuzz or melt-balls, and severe weight loss occurs in the fabric.

This invention provides a process for the removal of surface fuzz from fabrics comprising spun polyethylene terephthalate staple yarn, and for the subsequent removal of melt-balls from the fabric, without adversely affecting the desired fabric characteristics. Other provisions will appear hereinafter.

In accordance with the present invention, textile fabric woven from staple-spun yarns containing polyester fibers is singed to remove surface hairs with resultant formation of polyester melt-balls, the singed fabric is subsequently treated with a polyester-dissolving solvent to selectively dissolve the melt-balls with negligible effect on the fibers in the fabric, and the fabric is washed to terminate the solvent treatment after the melt-balls have been dissolved and before the fabric is damaged by the solvent.

The term polyester fibers as used herein encompasses both homogeneous mixtures and heterogeneous blends of various classes of polyester fibers and mixtures of polyester fibers with cellulosic fibers in which the polyester component comprises at least 20%, by Weight, of the blend.

The singeing treatment may be performed according to any thermal method known in the art. Preferably, the singeing treatment comprises passing the fabric to be singed near an open gas-flame in such a manner as to eliminate surface hairs of the fabric. Such treatment will produce polyester melt-balls which are usually from approximately l.1 to 6 times the diameter of the filament of which they are a part, and which appear on the fabric at a frequency of approximately 5000 to 20,000 per square inch (775 to 3100 per cm.

Unexpectedly, it has been found that these melt-balls can be dissolved preferentially, without dissolving the remainder of the polyester fibers to any appreciable extent, with polyester-dissolving acidic compounds when used in certain combinations of solvent concentration, temperature and duration of fabric treatment. The meltballs are quickly and thoroughly dissolved and the fibrous portion of the material is left unscathed in spite of the large volume and lack of porosity of the melt-balls. Thus, under preferred conditions, the melt-balls are removed and no appreciable weight loss occurs in the fabrics.

In the process of the present invention, solvents used to remove polyester melt-balls from the singed fabric include both inorganic and organic compounds which, as their primary function, affect the dissolution of polyester material, although they may possess to a small extent as secondary function, such as the potential for molecular chain scission through hydrolytic mechanisms. In view of this requirement, caustic solutions, although possessing a hydrolytic function in use with polyesters, produce no useful preferential dissolving effect on singed polyester fibers and melt-balls associated therewith, and are to be avoided in the process. Caustic hydrolyzes polyester fibers at their surface and destroys the fiber, consequently producing severe weight loss in the fabric.

Polyester textile fibers, in general, possess very high resistance to both mineral and organic acids. When using mineral acids as solvents in the process of the invention, extreme care must be taken with respect to choice of the acid, the concentration of the acid, and the temperature and duration of fabric exposure thereto. To illustrate, highly crystalline polyester fibers may be immersed in a solution of 70%, by weight, sulfuric acid in water at 40 C. for 72 hours with no consequent loss of strength in the fiber, although such exposure to concentrated (approximately 98%) sulfuric acid destroys the fiber. Further, polyester fibers may be exposed to a solution of 5%, by weight, hydrochloric acid in water at 100 C. for 24 hours with no adverse effects resulting, while nitric acid in practically any significant concentration destroys the polymer. As a further illustration, the fiber is not dissolved upon boiling for 1 minute in a solu tion of 90%, by weight, phosphoric acid in Water.

Of the mineral acids capable of dissolving the meltballs of singed fabrics of wholly polyester staple-spun yarn, slightly diluted sulfuric acid and mixtures of sulfuric acid with to by Weight phosphoric acid are preferred. It has been found that these acids, if used in the proper concentrations and temperatures shown herein below, within the limitations of the duration of fabric exposure thereto, effectively dissolve the melt-balls and produce no significant hydrolytic breakdown of the polyester molecules. Thus, the oriented and crystalline portion of the fibers in the yarn are relatively unaffected by the treatment and significant fabric weight loss and/or loss of strength will not result. Immersion of the singed fabric for from approximately 30 to 60 minutes in solutions of from approximately 70 to 80%, by weight, sulfuric acid in water, at from 20 to 30 C. is effective for melt-ball removal. If a less-concentrated sulfuric acid solution is used in the same manner, the melt-balls are not thoroughly removed; conversely, if a more-concentrated sulfuric acid solution is used in the same manner, significant molecular-chain breakdown occurs and, consequently, significant fabric weight loss occurs. Preferably the fabric is immersed in a solution of 78% sulfuric acid in water for 30 minutes at room temperature; When using mixtures of sulfuric and phosphoric acids, preferably the mixture comprises 20 parts, by volume, con= centrated sulfuric acid (approximately 96%, by weight, in water) and 80 parts, by volume, of a solution of 85%, byweight, phosproric acid in water, and the tempera ture and duration of exposure of the fabric to this mixture is the same as allowable for the sulfuric acid treat ment, supra. It deserves mention that when treating fabrics comprising blends of polyesters with cellulosics, mineral acids are to be avoided due to their destructive action on cellulosic fibers.

Many organic compounds are known to dissolve polyester fibers. A partial list of these includes phenol, o-chlorophenol, o-phenylprenol, tricresol, benzyl alcohol, nitrobenzene, and the mixtures: phenol-tetrachloroethane; phenol-trichloromethane; phenol-chlorobenzene; and phe- A similar fabric is prepared and finished in the same manner with the exception that just subsequent to the singeing treatment the fabric is immersed for three minutes in a solution of 88%, by weight, phenol in water, at room temperature, and thereafter removed from the phenol bath, rinsed in a solution of 2%, by weight, of sodium hydroxide in water, and heat-set at 140 C. to remove excess phenol. The fabric is examined and found to contain no melt-balls. The fabric has a smooth surface and excellent tactile characteristics. Similar treatment with o-phenylphenol instead of phenol is also found to dissolve the melt-balls without damaging the remainder of the fabric, and a corresponding improvement in fabric properties is obtained.

Example II An oxford fabric of 88 warp ends per inch (34.6 warp ends per cm.) by 48 picks per inch (18.9 picks per cm.) comprising commercial 1.5-denier per filament polyethylene terephthalate spun to 50/ 1 cc. for the warp and 15/1 cc. for the filling is finished according to standard commercial procedures including singeing. Upon singeing many small melt-balls develop on the surface of the noltoluene. Further, many organic compounds classified as carriers for polyester fibers i.e.-, organic compounds which swell polyesters to make them receptive to dyestuif penetration, have solvent properties when used in concentrated forms. Of the organic solvents mentioned,

phenol and o-phenylphenol are preferred for use in the new process especially for treatment of fabrics comprising blends of polyester and cellulosic fibers. At room temperature, concentrations by weight of phenol or ophenylphenol in water of from approximately 80 to 90% and a duration of exposure of fabrics thereto of from ment for the removal of melt-balls follows the fabric singeing operation. It is noteworthy that the fabrics, prior to solvent treatment and subsequent to singeing, preferably should not be exposed to high temperature such as those encountered in dyeing or scouring operations. It is believed that these high-temperature operations promote incipient crystal formation and encourage crystal growth in the polyester melt-balls, thus making them more resistant to solvent action.

The solvent may be applied to' the fabrics in numerous ways; for example, the fabric may be plunged into a solvent-containing vat or it may be immersed into the solvent by means of a commercial jig.

The invention is further illustrated by the following examples of preferred embodiments although it is not to be restricted thereto:

Example I fabric. The fabric is immersed for a period of thirty minutes at room temperature in a solution of 78%, by weight, sulfuric acid in water. After removal of the fabric from the sulfuric acid bath and washing to remove the acid, the fabric is examined and found to contain no melt balls. No appreciable loss in fabric tear-strength occurs as a result of the sulfuric acid treatment and the fabric so treatedexhibits excellent tactile characteristics.

Fabrics produced in accordance with this invention, upon dyeing, exhibit a uniformly colored appearance which Was heretofore unattainable in singed polyester fabrics. Fabrics which were dyed subsequent to being singed exhibited a speckled appearance which was directly associated with the presence of melt-balls as aforesaid. Many finishers were forced to singe dyed fabrics to avoid the severity of the splotches. Although this pro cedure alleviated the situation somewhat, melt-balls were still produced in the dyed fabric and these melt balls, being of greater diameter than the base filament were of a darker color than the base filament. By the process of this invention, melt-balls are thorougrly removed and the fabrics, upon dyeing exhibit a uniformly colored apearance.

A further advantage is apparent in the process of this invention. As stated, to lessen the severity of the speckled appearance resulting from dyeing fabric subsequent to singeing, many manufacturers dye the fabric prior to singeing. Since the fabric must be completely dry before singeing there necessarily exists a significant hold-up time between the dyeing and singeing operations. By the new process the fabric may be singed immediately subsequent to its fabrication and thus no such delay exists. Further, the fact that uniform dyeing is now achieved when the singeing operation precedes the dyeing operation introduces increased flexibility for maximum efiiciency and favorable economics in mill operation.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. In the finishing of textile fabric woven from staplespun yarns containing polyester fibers, the process which comprises singeing the fabric to remove surface hairs with resultant formation of polyester melt-balls, subsequently treating the singed fabric with a polyester-dissolving acidic solvent at 20 to 30 C. to selectively dissolve the melt-balls with negligible effect on the polyester fibers in the fabric, and washing the fabric to termimate the solvent treatment after dissolving the melt-balls and before damaging said fibers.

2. A process as defined in claim 1 wherein said solvent is 80% to 90% by weight of phenol in water and the fabric is treated with the solvent for 3 to minutes.

3. A process as defined in claim 1 wherein said solvent is 80% to 90% by weight of o-phenylphenol in water and the fabric is treated with the solvent for 3 to 30 minutes.

4. A process as defined in claim 1 wherein said solvent is to by weight of sulfuric acid in Water and the fabric is treated with the solvent for 30 to 60 minutes.

5. A process as defined in claim 1 wherein said solvent is a mixture of sulfuric acid with 80% to 90% by weight phosphoric acid in water and the fabric is treated with the solvent for 30 to 60 minutes.

-6. A process as defined in claim 5 wherein said solvent is a mixture of 20 parts by volume of concentrated sulfuric acid and 80 parts by volume of by Weight phosphoric acid in water.

7. A process as defined in claim 1 wherein said fabric is a blend of polyester and cellulosic fibers, the solvent is 88% by weight of phenol in water, and the fabric is treated with the solvent for approximately 3 minutes at room temperature.

6/1950 Great Britain. 7/ 1960 Great Britain.

ROBERT R. MACKEY, Primary Examiner. 

